Studies are proposed to characterize the enzymes of cyclic nucelotide synthesis (adenylate cyclase and guanylate cyclase) and degradation (cyclic AMP phosphodiesteriase and cyclic GMP phosphodiesterase) in cultured pigment epithelium from normal rats and RCS rats with hereditary retinal degeneration. Various extracellular agents that may modulate cyclic nucleotide metabolism in vivo will be evaluated for their effects on cyclic nucleotide metabolism in cultured pigment epithelium. These studies will help in our understanding of the cell biology of the pigment epithelium and will help to determine if the phagocytic defect in the RCS pigment epithelium is associated with an abnormality in cyclic nucleotide metabolism. Similar studies will also be done on pigment epithelium cultured from normal postmortem human donor eyes and the results should prove useful in evaluating pigment epithelium cultured from donor eyes of patients with hereditary retinal degenerations.